IPv4
IPv4 addresses consist of four numbers between 0 and 255 that are separated by a full stop, for example, 192.168.0.14. The network addresses are divided up into different classes (Class A to C) depending on how many computers can be located in a network.
Certain ranges are reserved for operating local networks:
•Class A: 10.x.x.x (for networks with up to 16.5 million PCs)
•Class B: 172.16.x.x to 172.31.x.x (for networks with up to 65534 PCs)
•Class C: 192.168.0.x to 192.168.255.x (for networks with up to 254 PCs)
These addresses have no validity on the Internet. This means that data packets with this kind of sender or recipient address cannot be sent over the Internet. However, they can be used in local networks without restriction. The benefit of this is that if data from a local network configured in this way comes in contact with the Internet, none of the data on the computers in the local network can leak out or be accessed externally.